The present invention relates generally to a mounting arrangement for a print engine, and more particularly, to such a mounting arrangement for use within a system for printing paper sheets wherein the sheets are tranported past an ink jet print head comprising a portion of the print engine.
A printing system for printing a plurality of moving sheets, typically includes unprinted sheets held in storage bins, a means for printing the sheets with ink, and drying apparatus. One example of such a system is a duplicator. Optional components such as a stacker, an inverter, a collator, or the like may be provided, and the system also includes means for transporting the sheets from one station to the next. The printing means may be an ink jet printer that deposits liquid ink upon a paper sheet in droplets as the sheet is moved by the transport means past the print head.
The print head itself represents one component of a larger print engine, which may include a plurality of print heads arrange to provide selected coverage of the sheet with ink at any loction thereon, along with fittings for connection of the heads to ink supplies, electrical control wiring, and the like. The print engine is mounted near the sheet transport path, which is typically defined by a movable belt upon which the sheets are carried. As the sheets move past the individual print heads, ink droplets are discharged onto the sheets for printing.
During operation of the printing system, it is occasionally necessary to gain access to the side of the print heads adjacent the transport path for servicing or inspection purposes. It may also be necessary from time to time to gain access to the transport path at the location of the print heads for clearance of paper jams. Accordingly, as shown in U.S. Pat. No. 4,080,607 issued March 21, 1978 to Van Bremen et al., a print engine mounting is provided in which the print engine is connected to the apparatus frame in part by a simple hinge. When access to the underside of the print heads is required, the engine is simply pivoted about the hinge.
While a simple access system such as that shown in Van Bremen et al. is effective for providing access to the print heads and transport path, the alignment achievable between the print heads and transport path in subject to change over the lifetime of the apparatus. Of course, it will readily recognized that such alignment is critical, since it will determine whether the print applied to each passing sheet is in proper registration with the sheet with respect to side margins along the sheet and the skew angle of the print upon the page. Further, unless distance between the print head and the sheet surface is properly maintained, the quality of the print upon the sheet will be adversely affected.
It is possible during assembly of the printing apparatus to take great care in properly aligning the print engine with respect to the transport path. Such an approach makes assembly of the apparatus tedious, time consuming, and more expensive, and requires that great care be taken in handling the equipment during shipping, operation, and servicing or inspection of the print engine to insure that proper alignment is maintained. Where provision is made for pivoting the print engine away from the transport path, such as is shown in Van Bremen et al., great care must also be taken in performing the pivoting operation or else inadvertent misalignment of the print engine with respect to the transport path may occur.
One alternative approach for providing alignment of a print head with respet to a transport system, in which alignment is made following assembly of the printing apparatus, is shown in U.S. Pat. No. 3,580,515, issued May 25, 1971 to Cassill. The printing apparatus includes a plurality of print heads supported by a pair of stepped supporting members disposed on either side of a moving paper web. A planar surface is disposed near one of the supporting members, with the individual print heads being urged against the planar surface to keep them in proper registration with the web. A mechanism is provided for shifting the planar surface so as to adjust the skew angle of the heads or to adjust the side margins defined upon the web as it is printed. This approach is limited, however, in that it does not provide any means of access to either the print heads or the paper transport path, short of removing the individual heads from the mounting arrangement. Moreover, no means is provided for adjusting the displacement of the print heads from the surface of the web to be printed.
What is needed, therefore, is a print engine mounting arrangement in which easy access is provided to both the print heads incorporated therein and to the sheet transport path. Such a mounting arrangement must also be capable of providing a means of adjustment of the print heads with respect to the sheets, including adjustments in skew angle, side margins and distance of the print heads from the surface of the sheets. Such adjustments should be capable of being made not only at the time of manufacture of the apparatus, to provide greater tolerances during assembly, but also after the apparatus has been placed in service.